The present invention concerns the preparation of shields and/or clamping rings in a physical vapor deposition chamber in order to increase shield adhesion and thereby achieve particle reduction in the chamber.
In physical vapor deposition (PVD) processes a target material, for example titanium tungsten, is bombarded by gaseous ions, for example argon ions. Material from the target is dislodged and sputters onto a workpiece. The workpiece is generally a semiconductor wafer, but may be, for example, a magnetic disk or a flat panel display.
A PVD chamber generally includes shields in the area immediately around a workpiece. The shields reduce the deposit of excess material sputtered from the target from contaminating the remainder of the PVD chamber. In addition, a clamping ring for the workpiece may also be present. Excess sputtered material will also deposit on the clamping ring.
For many types of sputtered materials, the build-up of excess material on the shields and/or clamping rings eventually results in flaking of the excess deposited material, producing particles in the chamber. At this point it is usually necessary to service the PVD chamber by replacing the shield and/or clamping ring. If shield or clamping ring replacement needs to be done at approximately the same time as target replacement, the servicing of the shield or clamping ring may be performed without loss of operation time. However, if the shield needs to be replaced much more often than the target, this can result in extra down time of the system which can seriously impair production throughput. It is desirable, therefore, to seek ways to reduce flaking and thereby lengthen the time between shield replacements.